Investors are today closely watching the much-anticipated introduction of a colossal piece of European Union (EU) legislation which aims to apply lessons from the financial crisis nearly a decade ago.

The revamped version of Europe’s Markets in Financial Instruments Directive — often referred to as Mifid II — is due to come into effect, impacting every corner of the continent’s financial services system.

Bankers have been working through the night to iron out last-minute hitches before today’s launch with the new rules are already a year late due to their complexity, with regulators having to issue 11th-hour guidance to banks and financial firms to avoid freezing up trades as well as calming nerves of those not yet fully compliant.

The new regime shines a spotlight on the innards of stock, bond, commodity and derivatives markets by forcing banks, asset managers and traders to report detailed information on trillions of euros in transactions.

However, the UK and Germany have been granted last-minute reprieves to the continent’s biggest futures exchanges to implement the rules.

London’s Liffe derivatives exchange and the London Metal Exchange were given an extra 30 months to comply with rules, while Eurex, the Frankfurt-based futures exchange owned by Deutsche Börse, was given a similar late reprieve last night by BaFin, Germany’s national regulator.

Late last year banks were pushing to delay a key part of the imminent legislation which requires market participants to have their own unique 20-character alphanumeric code, known as a Legal Entity Identifier (LEI).

Mifid II could see global investment research spend fall by as much as $1.5bn annually when the rules come into force in January, according to management consultancy Oliver Wyman estimates.

Banks have been pushing regulators to grant a grace period of several months after Mifid II comes into force.

What will happen to the Mifid II in the UK after Brexit?

It’s stil not known whether the UK’s financial services industry will continue to operate under Mifid II rules after it quits the trading bloc in March 2019.

Eurex yesterday successful argued that the exit of the UK — Europe’s largest market for clearing derivatives — from the EU introduced too much uncertainty given that Britain may not be bound by the rules once it leaves.

A Eurex spokesperson said:

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Brexit is a game changer. We share industry concerns around financial stability regarding the open access provisions of Mifid II.

Law firm Linklaters wrote in a blog last year:

It is possible that the UK may decide to keep the MiFID II regime largely intact after it withdraws from the EU. Some of the rules are already in place, and many of the changes have been made at the UK’s behest. This would potentially make it easier for UK firms to access the EU market through the third-country provisions of MiFID II and MiFIR, on the basis of equivalence.